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| #6956 (Received by flhurricane at: 4:39 AM 01.Sep.2004) TCDAT1 HURRICANE FRANCES DISCUSSION NUMBER 30 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT WED SEP 01 2004 REPORTS FROM THE LATEST AIR FORCE RESERVE HURRICANE HUNTER MONITORING FRANCES SHOW MAXIMUM FLIGHT-LEVEL WINDS AT 700 MB OF 123 KT...DOWN A LITTLE FROM THE EARLIER FLIGHT. HOWEVER...THE CENTRAL PRESSURE HAS DROPPED TO 935 MB. BASED ON THIS...THE INITIAL INTENSITY WILL REMAIN 120 KT FOR THIS ADVISORY. THE WSR-88D AT SAN JUAN SHOWS THAT FRANCES HAS CONCENTRIC EYEWALLS...AND THE AIRCRAFT DATA SHOWS THREE CONCENTRIC WIND MAXIMA. INDEED...ON THE LATEST PASS THROUGH THE SOUTHEASTERN QUADRANT THE HIGHEST WIND WAS IN THE MAXIMA ASSOCIATED WITH THE OUTER EYEWALL. THE INITIAL MOTION IS A WOBBLY 285/15. FRANCES REMAINS ON THE SOUTH SIDE OF A SUBTROPICAL RIDGE WHICH LARGE-SCALE MODELS FORECAST TO WEAKEN SOMEWHAT OVER THE NEXT 72 HR. THIS SHOULD ALLOW THE HURRICANE TO MOVE WEST-NORTHWESTWARD IN THE GENERAL DIRECTION OF THE FLORIDA PENINSULA. DYNAMICAL MODEL GUIDANCE AGREES WITH THIS SCENARIO...EXCEPT FOR THE GFDL WHICH CONTINUES TO CALL FOR A UNREALISTIC LOOKING MOTION TOWARD THE NORTHWEST. THE OFFICIAL FORECAST THROUGH 72 HR IS SHIFTED A LITTLE WEST OF THE PREVIOUS TRACK BASED MAINLY ON THE INITIAL POSITION AND MOTION AND IS ON THE LEFT SIDE OF THE DYNAMICAL GUIDANCE. AFTER 72 HR...THERE IS DIVERGENCE IN THE GUIDANCE AS A SHORTWAVE RIDGE DEVELOPS NORTH OF FRANCES OVER THE EASTERN UNITED STATES. THE OFFICIAL FORECAST TRACK FOR THAT TIME IS SHIFTED TO THE SOUTHWEST OF THE PREVIOUS TRACK...ALTHOUGH NOT AS FAR AS THE UKMET WHICH MARCHES FRANCES WESTWARD ACROSS CENTRAL FLORIDA AND INTO THE GULF OF MEXICO. THE INTENSITY FORECAST IS MODIFIED ONLY SLIGHTLY FROM THE PREVIOUS PACKAGE. UPPER-LEVEL WINDS ARE FAVORABLE THROUGH AT LEAST 36-48 HR...SO FRANCES SHOULD REMAIN STRONG. A SLIGHT WEAKENING IS INDICATED AT 72 HR BASED ON LAND INTERACTION AND SOME POSSIBLE WESTERLY SHEAR. THE MAIN CONTROLLING FACTOR ON INTENSITY WILL BE THE STRUCTURE OF FRANCES AND CONCENTRIC EYEWALL CYCLES...BOTH OF WHICH ARE DIFFICULT AT BEST TO TIME. GIVEN THE CURRENT STRUCTURE OF THE HURRICANE...CHANGES IN INTENSITY WILL LIKELY BE RELATIVELY SLOW TO OCCUR. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 01/0900Z 21.2N 68.5W 120 KT 12HR VT 01/1800Z 22.0N 70.6W 125 KT 24HR VT 02/0600Z 23.2N 72.9W 125 KT 36HR VT 02/1800Z 24.3N 74.8W 130 KT 48HR VT 03/0600Z 25.5N 76.6W 130 KT 72HR VT 04/0600Z 27.0N 79.5W 125 KT 96HR VT 05/0600Z 28.5N 81.5W 85 KT...INLAND 120HR VT 06/0600Z 31.0N 84.0W 35 KT...INLAND |
